Conventionally, coil components such as surface-mounted planar coil elements, etc. have been widely used for electric appliances such as household apparatuses, industrial apparatuses, and so on. Especially, in small portable devices, with the fulfillment of functions, there has occurred a need to obtain a plurality of voltages from a single power source in order to drive the respective devices. Here, the surface-mounted planar coil element is used also for this power source purpose, or the like.
Such a coil component is disclosed in, for instance, Japanese Unexamined Patent Publication No. 2005-210010. In the coil component disclosed in this document, planarly spiraled air core coils are provided on front and rear surfaces of a board respectively, and the air core coils are interconnected by a through-hole conductor provided to pass through the board at magnetic core portions of the air core coils.